1. Field of the Invention
The present invention relates to a plasma display panel, and more specifically to a plasma display panel of the dot matrix type, which is now expected to be widely used in personal computers and office work stations which are now remarkably advancing, and in flat panel type television receivers expected to further develop in future.
2. Description of Related Art
In Japanese Patent Application No. Hei 1-108003 filed on Apr. 26, 1989, the applicant proposed a color plasma display panel which includes first and second insulating plates such as glass plates separated from each other to form therebetween a discharge space, which is divided by a spacer having a partition wall in the form of a grid or a lattice so that the discharge space is partitioned into a number of pixels. On an inside surface of the first insulating plate, a plurality of row electrodes are formed in such a manner that each of the row electrodes is aligned with a corresponding partition wall extending in a row direction, so that each pair of adjacent row electrodes face to one pixel, and on an inside of the second insulating plate, a plurality of column electrodes are formed to pass through a center portion of one array of pixels arranged in one column direction. A phosphor is deposited on the column electrode within each of the pixels, and a discharge gas is filled into each of the pixels defined by the first and second insulating plates and the grid-shaped partition wall of the spacer.
If a high voltage pulse is applied between one row electrode and one column electrode, an electric discharge is created within a pixel designated by the row electrode and the column electrode applied with the high voltage pulse. Thereafter, the electric discharge is maintained by applying an alternate current voltage between a pair of row electrodes facing to the pixel in which the electric discharge has been created by the high voltage pulse. This discharge is called a maintaining discharge. In addition, the discharge generated and maintained between electrodes located on the same substrate is called a surface discharge. This discharge generates a ultraviolet light, which excites the phosphor. As a result, a visible light is generated by the excited phosphor. This generation of the visible light can be stopped by reducing or eliminating the alternate current voltage applied between the pair of adjacent row electrodes.
Therefore, a dot matrix display can be realized by locating the row electrodes and the column electrodes in the form of a matrix so that the row electrodes and the column electrodes intersect perpendicularly to each other. In addition, if the phosphor is divided into three primary colors, so that each of the pixels is filled with selected one of the three primary colors, a color plasma display can be realized.
In the above mentioned plasma display panel, however, a surface of the phosphor receiving the ultraviolet light generated by the electric discharge is different from a surface of the phosphor emitting the visible light to a viewer, namely, in a display direction. In this case, the magnitude of the light emitted toward the display direction, namely, the brightness, depends upon the thickness of the phosphor. Specifically, if the phosphor is thicker or thinner than an optimum thickness, the brightness will decrease. On the other hand, the display is required to have as high brightness as possible, in order to give a sufficient distinction. Therefore, the prior proposed plasma display panel has been required to have the phosphor of the optimum thickness. However, it is very difficult to deposit a phosphor of a constant thickness uniformly throughout a whole surface of the display panel. Particularly, difficulty has been increased in the case of depositing three primary color phosphors of uniform thickness to different pixels.